The major purpose of a horseshoe is to protect the horse's hooves against injury and to add traction. In a race horse, a properly designed horseshoe is an important piece of equipment which can enhance the horse's racing performance and can add years to the length of the horse's racing career. When a horse is running its hooves hit the ground with a great deal of impact. Under certain running conditions, a horse's stride can cause all of its weight to land on one hoof. This impact is transmitted through the hoof and up through the horse's legs. When a horse runs without shoes, its hoof deforms upon impact and absorbs a portion of the impact forces. A horse that runs with shoes may experience soreness in his hoofs and legs partially because the rigid shoe inhibits the natural deformation of the hoof. Unless great care is taken to protect the horse's legs and hooves against impact and vibration damage, the horse can develop sore feet and lame legs due to corns, cracks and other damage.
In the past a number of different horseshoes have been developed that provide cushioning for a horse's hooves. In many of these horseshoes, cushioning has been provided by merely placing leather, rubber or even plastic pads in a variety of embodiments between the horse's hoof and the metal shoe. This may be undesirable because the presence of a resilient material between the hoof and the shoe may cause the horseshoe nails to vibrate loose so that the shoe may slide on the hoof or even come completely off. Furthermore, the metal shoes have usually been rigid so that the horse's hoof is only cushioned against the vertical component of the forces experienced during running. As a result, few of these previous designs have been entirely satisfactory.
In current practice, a high percentage of horseshoes are made of a flexible metal such as aluminum alloy or other lightweight metals which will deform in a direction transverse to the horse's hoof to permit a degree of flexibility to the hoof. They also have the advantage of being lightweight so that they may be easily carried by the horse.
To add traction, these aluminum plate shoes usually have a steel toe calk and heel calks projecting toward the ground. To further improve traction, some shoes have included individual rubber cleats bonded to the bottom of the shoe.
One such horseshoe is shown in U.S. Pat. No. 2,622,685 to Dixon entitled "Flexible Racing Horseshoe" which provides an aluminum base with a plurality of peripheral flanges and an L-shaped toe calk riveted to the toe portion of the plate. A number of separate rubber cleats are bonded along the bottom of the shoe. The aluminum plate provides lateral flexibility to the horseshoe and the flanges provide a controlled amount of lateral flexibility to the rubber cleats. The Dixon horseshoe does not disclose any cushioning between the aluminum plate and the horse's hoof but relies entirely upon individual cleats to absorb the vertical component of the impact forces experienced by the horse's hoof. Eliminating any cushioning between the plate and the hoof can be unsatisfactory because the pressure of a metal plate directly against the horse's hoof can still cause soreness and other hoof and leg damage. Using individual cleats can be unsatisfactory because they can easily jar loose. When this happens the entire shoe must be replaced.
A second U.S. Pat. No. 3,090,718 to Dixon entitled "Flexible Cushioned Horseshoe" provides a similar overall design but eliminates the peripheral flanges. In this second patent Dixon recognizes that he did not previously appreciate the extent to which cushioning aids a horse. To add further cushioning, he tapers the heel portion of the aluminum plate to provide a greater rubber thickness in the heel area. The second Dixon patent, however, still does not provide any cushioning between the horse's hoof and the aluminum plate and still uses individual cleats.
In the past horseshoes were designed differently for the front and hind hooves of a horse. The hind shoes usually include a metal mud calk on their outside heel portion to add traction. These mud calks can be cast right into the plate or they can be screwed into the plate. The inside heel portion of each hind shoe usually included two metal blocks to control the horse's stride and prevent running down. A horse will run down either from a natural tendency peculiar to a particular horse or to compensate for sore front hooves by bringing its hind hooves farther forward and digging in too hard. This can cause the rear part of its hind ankle to rub against the running surface and chafe or even bleed. The use of blocks on the inside of the hind shoe raises the hoof off the running surface and adds traction to avoid running down. Thus the left and right hind shoes are different from each other and different from the front shoes. This adds to the cost and difficulty of providing proper shoes for a horse.
There is a need for a horseshoe that will accommodate the natural lateral flexibility of the horse's hoof and provide vertical cushioning directly to critical areas of the horse's hoof while still maintaining a secure contact surface between the remainder of the hoof and the horseshoe. There is also a need for a horseshoe of a single design that can be used on any hoof.